1. Technical Field
The invention is related to the field of optics, and more specifically, to the field of adaptive optics, active optics, platform and image stabilization for extended source applications such as astronomical, terrestrial, marine, space imaging systems.
2. Related Technology
Adaptive and active optics systems are intended to measure and compensate, in near real time, aberrations introduced in an optical wavefront as it passes through a medium, or from jitter induced by motion in a platform. In these systems, a wavefront sensor is employed to measure the phase front of light. These phase measurements provide information about the phase front that are attributable to the medium and can be used with deformable optics to correct or minimize the wavefront aberrations. Wavefront sensors can measure both static and dynamic aberrations. There are a variety of wavefront sensors, including interferometric sensors, lenslet arrays and wavefront curvature sensors, but they are not well suited to operate with extended sources and are typically used for point sources only.
A Shack-Hartmann wavefront sensor is a specific type of wavefront sensing that employs an array of lenslets to break the wavefront into small pieces and measure local tilt of a wavefront. The development of Shack-Hartmann sensors is described in Platt, B. C., Shack, R., “History and Principals of Shack-Hartmann Wavefront Sensing”, Journal of Refractive Surgery, Vol. 17, September/November 2001, pp. S573-S577.
A phase-diversity or curvature wavefront sensor measures the curvature of a wavefront by measuring intensity differences of the light at two planes and then calculates the wavefront phase. U.S. Pat. No. 7,554,672 to Greenaway et al. discloses an example of a phase-diversity wavefront sensor.
Other methods for measuring and correcting for wavefront aberrations are described in S. W. Teare and S. R. Restaino, Introduction to Image Stabilization, SPIE Press, Tutorial Texts in Optical Engineering, 2006 and in John W. Hardy, Adoptive Optics for Astronomical Telescopes, Oxford University Press, 1998.